Several shallow water studies of fish behavior have used a methodology called the tracking transducer. The principle of tracking radar, aligning the antenna beam with a target, was applied with an acoustic split-beam transducer and dual-axis rotators for tracking individual fish over long periods of time. Initial studies with active acoustics have evolved an acoustic tag tracking method that is proposed for tracking both juvenile salmon and pelagic sharks. The following paper (See document link below) documents the present state of the tracking methodology and proposes methods to track salmon, sharks or other species both with echoes and by using acoustic tags that will allow behavior, abundance and associated pelagic assemblages to be determined.

The system used in this study is a BioSonics DT Series split beam sonar, which is used to identify an individual fish echo and to determine three-dimensional position of a fish target, with a transducer mounted on a high-speed dual-axis rotator. The split beam sonar detects the deviation of the target from the transducer’s beam axis and sends this information to a tracking computer. The tracking computer uses a predictive tracking algorithm to align the transducer axis to the target using high-speed motors of the dual-axis rotator. At the same time data regarding the fish position and movement, and Target Strength (acoustic size of fish) are recorded to hard disk. Fish tracks over 50 meters have been obtained with this tracking system.

Digital active fish tracking sonars (AFTS) were used in 2001 to study fish movement in response to intake occlusion plates at The Dalles Dam on the Columbia River. AFTS provides three-dimensional fish tracks by aligning the axis of the split-beam transducer with a fish target. High-speed stepper motors move the transducer so that a tracked target remains on-axis. Occlusion plates with J-extensions covered the top half of the turbine intakes to produce a fish friendly near-dam environment. Two AFTS were positioned at the center of Main Unit 1, one each for monitoring plates IN and OUT conditions. The occlusion plates had pronounced effects on fish movement along the dam. They appeared to decrease westward movement, decrease movement toward the dam (especially in front of the turbine intake), and decrease downward movement toward the turbines. Fish fate into a particular area was determined using Markov chain analysis. The sluiceway (a safer passage route) zone of influence was larger with the occlusion plates IN than OUT. Moreover, the probability of passage out the turbine/bottom sides of the sample volume was about 50% lower with occlusion plates IN than OUT.

The objectives of the sonar tracker study were as follows:
1. Describe smolt movements in terms of observed fish directions and movement fates, with and without J-occlusions in place. Fates are probabilities to which side of the sample volume a tracked fish will exit.
2. Assess the following specific hypotheses about smolt movements:

a) The zone of influence of the sluiceway as determined by fate probabilities will be larger with J-occlusions than without;
b) The overall probability of passage toward the spillway (west) will be higher with J-occlusions than without;
c) The overall probability of passage toward the turbines will be lower with J-occlusions than without.

In 2001 at The Dalles Dam, prototype turbine intake occlusion plates with 8 m “J”-extensions were evaluated as a new means of preserving juvenile salmon. As part of the overall J-occlusion evaluation effort, researchers collected data on smolt movements in front of Sluice 1-2 from April 24 to June 1, 2001, using two digital acoustic fish tracking sonars (AFTS) developed by BioSonics. The sonar tracker data will be useful to interpret and explain the J-occlusion performance data, which will be the “bottom-line” for decisions about the J-occlusions.

The general approach taken during this study was to use an active fish tracking sonar (AFTS) system to intensively sample fish movements in the region immediately upstream of a sluiceway entrance at The Dalles Dam. The components of an AFTS system include a BioSonics DT Series 200 kHz digital split-beam echo sounder, a 7° split-beam transducer, two high-speed stepper motors for dual axis rotation, a controller unit, a laptop computer, a desktop computer, and cables.

In summary, effects of the J-occlusions on smolt movements were evident as noticeable, distinct differences in movement patterns between the IN and OUT conditions. Mean fish velocities, movement proportions, and fate probabilities all demonstrated differences between J-occlusions IN and OUT. Generally, the J-occlusions appeared to cause fish in the nearfield of Sluice 1-2 to decrease westward movement, decrease movement toward the dam, and increase upward movement in the water column. If these patterns translate to passage, then we would expect the J-occlusions to result in decreased turbine and increased sluiceway fish passage rates.

BioSonics work at Wells Dam on the Columbia River has spanned over two decades. Fixed-location hydroacoustic techniques have been used to describe the temporal and spatial characteristics of the downstream salmonid migration at Wells Dam every spring and most summers since 1981.

Through the years, study objectives have changed from early baseline monitoring of fish distributions (seasonal run timing, vertical, horizontal and diel distributions) to the intensive studies required to develop and verify the bypass system. Currently the system at Wells provides a “near real-time” analysis of acoustic data with the ability to provide fish managers access to these data at any time from any location. This fully automated system results in cost savings of more than tenfold compared to similar fully manned efforts.

Wells Dam is the first dam that over two million smolts must pass during annual outmigrations through the Columbia River to the Pacific Ocean. Douglas County Public Utility District (DCPUD) owns and operates the dam, and is responsible for protecting anadromous fish that migrate past Wells Dam.

DCPUD developed the smolt bypass system at Wells Dam that is based on spill intake baffles. Wells is a hydrocombine with the spillway located directly above the turbine intakes. Spill intake baffles increase flow velocities in the forebay, thereby creating water currents which attract smolts. Once entrained in this attractant flow, smolts enter the bypass and migrate through the dam in bypass flow instead of turbine flow. A relatively small amount of spill, properly baffled, is equally or more effective at bypassing smolts than is a large amount of spill that is not baffled. Diverting smolts from turbines will increase smolt survival rates and help restore anadromous fish populations.

The fixed-location hydroacoustic system, manufactured by BioSonics, included echo sounders, multiplexers, and transducers. The transducers were sequentially sampled using multiplexers. The transducer produced a sound field that is projected up and slightly upstream. As a fish moves toward the dam, it enters the sound field at a greater distance from the transducer than the distance at which it leaves. This pattern of movement produces characteristic linear trace slopes, which can be interpreted as corresponding to downstream movement. Other species may reside in the near surface waters and be able to swim upstream or hold position. These behaviors will produce a completely different type of trace that is easily recognized.

Automation of the collection and analysis of acoustic data at Wells dam has reduced manpower costs, reduced subjectivity and increased consistency, and has provided near real-time results.

Fish exclusion and monitoring of a blast containment area were studied using electrofishing techniques, electrical barrier and hydroacoustic techniques on the Rogue River near Medford, Oregon, in the summer of 2000. The objectives of the project were to determine the abundance of fish before fish exclusion, to exclude fish from the effective blast area, to determine efficiency of fish exclusion and to document blast-caused fish mortality.

Researchers from Smith-Root, Inc. used an electrofishing boat and an electric fish barrier, which emitted small electric pulses, in an attempt to exclude fish from the effective blast area. Hydroacoustic surveys were conducted by BioSonics before, during and after these exclusion measures, to determine the effectiveness these measures had on excluding fish from the blast area. Both mobile and stationary surveys were conducted using a BioSonics DT Series echosounder system, in order to measure fish presence, location and behavior.

Analysis of the data collected during the project was conducted to determine the effectiveness of the various methods for fish exclusion. Electrofishing was found to be successful in greatly reducing the number of fish at the site, and in moving fish downstream past the electric barrier. By the time the barrier had been turned on, 70% of all fish counted had moved downstream, away from the containment area. The electric barrier was 100% successful in keeping adult salmonids from reentering the containment area. Small fish were observed in the site moving upstream after it was turned on. Those fish were moving though the deepest part of the river, where the power from the barrier was weakest. A range of fish was excluded from the site, from about 0.1 m (4.3”) to 0.5 m (19.8”) in length. BioSonics equipment was found to be an effective measure for determining fish abundance before and after the blast, and for analyzing the fish exclusion techniques used throughout the project.